Method and apparatus for manufacturing hermetically sealed electric switch



Feb. 24, 1959 E. MCCABE METHOD AND APPARATUS FOR MANUFACTURINGHERMETICALLY SEALED ELECTRIC SWITCH '7 Sheets-Sheet 1 Filed Sept. 4,1953 INVENTOR. IRA E. M? 6455 Feb. '24, 1959 1. E. M CABE 2,874,522

- METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLY SEALED ELECTRICSWITCH Filed Sept. 4, 1953 7 Sheets sheet 2 I72 /75 I I74- I C I; a: i."u I77 IN V EN TOR.

1959 l. E. M CABE METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLYSEALED ELECTRIC SWITCH Filed Sept. 4, 1953 '7 SheetsSheet 3 INVENTOR./RA 5. MS (ABE BY Qzf/r I. E. M CABE Feb. 24, 1959 PPARATUS FORMANUFACTURING HERMETICALLY SEALED ELECTRIC SWITCH Filed Sept. 4, 1953METHOD AND A 7 Sheets-Sheet 4 I IN VEN TOR. IRA 5 MS CABE flzzj sINVENTOR.

diff r I. E. M CABE METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLYSEALED ELECTRIC SWITCH Feb. 24, 1959 '7 Sheets-Sheet 5 Filed Sept. 4,1953 I IRA ii/61985 Feb. 24, 1959 Filed Sept. 4, 1953 7 Sheets-Sheet 6fiN V EN TOR.

m4 5.01s cnaz '7 Sheets-Shee t '7 Feb. 24, 1959 l. E. McCABE METHOD ANDAPPARATUSFOR MANUFACTURING HERMETICALLY sums ELECTRIC SWITCH Filed Sept.4, 1953 3 r: 5 1 mm a 7 F l .l v.

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United States Patent METHOD AND APPARATUS FOR MANUFAC- TURINGHERMETICALLY SEALED ELEC- rnrc SWITCH Ira E. McCabe, late of Chicago,111.; Cecil Z. McCabe,

Thomas P. "Crawford, and George D. McCabe, co-

executors of said Ira E. McCabe, deceased, assignors vto The MercoidCorporation, Chicago, 111., a corporafion of Delaware ApplicationSeptember 4, 1953, Serial No. 37 8,510

Claims. (Cl. 53-22) The invention relates to hermetically sealedelectric switches of the mercury contact type such .as may be actuatedby magnetic means or by tilting mechanisms and has reference moreparticularly to a novel method and to improved apparatus for carryingout the method in the desired sequence of steps for the production ofsaid mercury switches in an automatic manner.

Mercury switches designed for actuation by either magnetic means or bytilting mechanisms have been manufactured, in part, by machine withcertain operations being performed by hand such as the handling and.placement of the parts on the machine with certain steps in .thefinishing procedures also being performed by hand such as exhausting theair from the interior of the glass enclosure of the switch, substitutinga gas for reducing the are during operation, and injecting the mercury,all as clearly disclosed, for example, in the McCabe Patent No.1,872,070 and in the Hunciker Patent No. 1,882,613. The manualprocedures following the machine assembly of the switcli'par'ts withinthe glass enclosure and the handling of the product throughout thevarious manual operations has constituted an important item of cost inthe manufacture of theswitches. In the magnetically actuated types whichinvolve moving and spring tensioned .parts sealed within the switchenclosure, as in the Mo- Cabe Patents Nos. 2,325,785 and 2,442,981, themachine methods employed for sealing the operating mechanism have'soaifected the spring tensioned movable parts that 'in some instancescalibration and adjustment for" the parts after sealing have beennecessary in order to obtain the desired operation of the switch. Thishas been due to the high temperaturesrequired for the glass presssealing operation, which temperatures are developed over a period oftime, thus producing a transfer offthe heat ,to the switch elementsbeing sealed within the enclosure. One end of the glass enclosure isusually left open for possible and needed adjustments after sealing,said open end being subsequently sealed to prepare theswitch formercury.

'In the methods of switch manufacture as exemplified by'the abovepatents, the sealing by pressing molten glass about a portion of theenclosed switch structure, and the means resorted to for exhausting andfilling the switch interior with gas and mercury materially affected theoverall length of the completed switch. Furthermore, the usual method ofconnecting lead wires to the switch by soldering the leads to terminalsprotruding from the sealed portion also contributed to the overalldimension of the switch so that these factors precluded the possibilityof the manufacture of miniature, hermet- 'icaliy sealed, glass enclosedswitches of the size now made possible by this invention. i iAccordingly, an object of the invention is to provide a method andapparatus for manufacturinghermetically ,sealed, :glass enclosed mercuryswitches of an improved :type characterized by metal fend capsytoprovidea method apparati s :a1s dest:rib ed which .will ,produce said2,874,522 aten d F b- .1359

2 switches in miniature sizes heretofore impossible for this class ofelectric switch; and to provide a low cost manufacturing method whichwill employ relatively simple apparatus capable of automatic operationfor producing said switches on a quantity basis.

Another object of the invention resides in the pro vision orapparatus'for automatically assembling in an efiicient manner the partsof the present mercury switch which include a glass tube and metal endcaps, the glass tube housing the contact or contact operating mechanism,whereas the caps serve is terminals for'circuit connections, and whereinsaid apparatus will operate on a step by step procedure ofmachinemanufacture involving the automatic feeding of the several parts andtheir assembly in the proper order.

Another object is to provide automatic apparatus as above describedwhich will incorporate high frequency induction heating for fusing themetal end caps to the glass tube, thereby localizing the application ofheat for this purpose with the result that the time involved is somaterially reduced that detrimental effects upon the operating parts areeliminated whereby said parts can thus be accurately calibrated prior toassembly, said apparatus also incorporating additional means incombination with said high frequency induction heating for controllingcertain dimensional characteristics of the switch during the fusingoperation.

' Other objects of the invention are to materially reduce manufacturingcosts in the production of mercury switches of the present type, toimprove the method of exhausting the completed switch, "or filling thesame with gas, and the method of injecting the mercury into the switch.

With these and various" other objects in view, theinvention mayconsistof certain novel features of construction and operation, as willbe more fully described and particularly pointed outin thespecification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention andwherein like reference-characters are used to designate like parts--Figure 1 is a fragmentary top plan view of apparatus for assembling thevarious elements which comprise the present type of mercury switch, thesaid figure illustrating the several stations of theapparatus and themechanism .at each station for performing the steps of the presentmethod.

Figure 2 is an elevational view, parts being shown in I section, of adevice employed in the performance of a series of operations on theswitch, including the injection of an inert gas and the insertion ofmercury.

Figure 3 is a sectional view taken substantially along line 3-3 ofFigure 2.

Figure 4 illustrates in elevation the completed mercury switch, partsbeing broken away to show certain structural features.

Figures 5 and 6 are .views illustrating another type of mercury switchwhich may employ the improved method and apparatus of the invention forassembling the parts thereof.

Figure 7 isan elevational view, with parts being shown in section, ofthe mechanismcomprising station A of'the present apparatus.

Figure 8 is an elevational view, with parts being shown in section, ofthe mechanism comprising station E of said apparatus.

Figures 9, 10, 11 and 12 illustrate in detail the principal partscomprising the structure of station C.

Figure 13 is an elevational view illustrating the structure of station Efor sealing theassembled elements of the switch by induction heating,the parts of said structure being shown in position prior to a heatingoperation.

Figure 1.4 'is a view similar to Figure 13 butshowing is relativelysmall in size.

the parts comprising the structure of station E in a position for aheating operation.

Figure is a sectional view illustrating certain parts of station E,andshowing in particular the switch mechanism for controlling the highfrequency induction heating device; and I Figure 16 is a view on anenlarged scale illustrating in detail the relation of the assembledswitch elements when 4 located within the induction heating coils.

Figure 4 of the drawings illustrates one type of mercury switch whichmay be assembled by the method and apparatus of the invention, the saidswitch 20 comprising a top cap 21 of any suitable metal, a glass tube orcontainer 22, and a metal bottom cap 23, the said caps being fused tothe glass tube by induction heating in a manner to be described indetail. has fixed thereto an electrode 24 which in assembled The top caprelation depends centrally within the glass tube, terminating short,however, of the bottom cap so as to The bottom cap 23 is provided withan opening 26, as best illustrated in Figure 2, and which In accordancewith the invention the opening facilitates the flushing of the switchinterior with a gas and the injection of the mercury 25, whereupon theopening is closed by an iron pin 28 to complete the switch and which isthus ready for com- ;mercial use.

switch parts for uniting them to form a unit is carried out at station Eand the three stations following, namely, F, G and H, are provided withgas jets for directing gas flames onto the switch for annealing theglass container of the same. The completed switch is discharged atstation K.

Referring more particularly to Figure 7, which illustrates the structureof station A in detail, it will be observed that the turntable 30carries a number of part holders generally indicated by numeral 31 andconsisting of a cup member 32 which is fixed to the spindle 33, saidspindle being mounted by the member 34 for reciprocating movement,whereby the spindle can be elevated or lowered to properly position thecup member 'as the same is moved from station to station. At station Athe feeding mechanism for the top caps is so located with respect to theturntable that elevation of the part holder is not required.

Said feeding mechanism essentially consists of a platform 35 suitablysecured to and supported by the standard 36, said standard pivotallysupporting at 37 the lever 38 adapted to be cam actuated against thetension of spring 40. Said spring is housed in the recess 41 andtensions the pin 42, causing the same to project outwardly into contactwith the lever 38. The threaded plug 43 backs the spring and said plugis locked in adjusted position by the nut 44. The'chute 45 receives asupply of top caps 21 from a magazine feed, not shown, and from saidchute the caps in inverted position are presented to a sliding pushplate 46 operating in a grooved track 47 provided in the platform 35.The lever 38 is pivotally connected at 48 to the push plate and cammeans, not shown, are provided to cause retraction of the lever and pushplate to allow a cap 21 to be placed within the groove 47 in advance ofthe push plate. During the period the part holder 31, Figure 7, ispositioned at station A, the cam means will release the lever and thenpin 42 under the tension of spring 40 will produce clockwise movement ofthe lever and movement of the push plate to deliver the cap through theplatform opening 49 to the cup member 32 of the part holder.

The next operation of the apparatus is to produce an index positioningof the'turntable 30, which moves all the part holders to their nextadjacent station. Accordingly, the cup member 32 containing the top cap21, is moved to station B and a glass cylinder is deposited thereon bythe mechanism shown in Figure 8. The base plate 50 supports the standard51 which in turn suitably supports the platform 52. The member 53 may bepart of the platform or may be secured thereto by screws such as 54. Thetubular supply chute 55 for the glass tubes 22 is fixed to said member53 which has a vertical passage provided therethrough for receiving theglass tubes and for directing them to the apertured feed block 56. Saidfeed block 56 is mounted for movement between the platform 52 and member53 and is pivotally connected at 57 to the lever 58 pivoted at 59 to thestandard 51. Cam means, not shown, normally retracts the lever 58 andblock 56 to a point where the aperture in said block aligns with thepassage in the member and receives a glass tube. In said retractedposition the pin 60 is caused to compress the spring 61 located withinthe recess 62 and backed by the screw plug 63.

Upon arriving at station E the spindle 33 of the part holder enters thejaws 64 of the lifter 65 which includes a supporting rod 66 mounted forvertical reciprocating movement by the tubular member 67 which is fixedto the base 50. At a predetermined time after the holder spindle 33 hasentered the jaws 64, the lever 68 is actuated to elevate the lifter 65and through the spindle 33 the part holder is also elevated to locatethe cup member 32 thereof in close proximity to the underside of theplatform 52 and in alignment with the discharge opening 70. The lever 58is also actuated by the cam means, not shown, in a releasing directionpermitting the pin 60 to move the lever clockwise and the feed block 56forwardly until contact is made with the adjustment screw 71. The glasstube carried by the feed block is accordingly delivered through theopening 70 onto the top cap previously deposited in the cup member 32.After this assembling operation is completed the cam means functions toretract the lever 58 so that the feed block 56 is again located inposition as shown in Figure 8 and the part holder is lowered by similaractuation of lever 68, for which purpose the spindle 33 carries theterminal screw 72. By means of the lips on the jaws 64 the screw isengaged as the lifter is lowered and the part holder is actually pulleddown into its normal low position.

Following the operations taking place at station B as described, theturntable is again rotated to the extent of its indexing movement toprogress all the part holders one complete station. Therefore the partholder 31, containing a top cap 21 and a glass tube 22 in assembledrelation, is moved to station C for receiving a bottom cap 23. Thefeeding mechanism at station C is generally shown in Figure 1 withstructural details thereof being shown in Figures 9 to 11 inclusive. Inmany respects the mechanism of station C is similar to that described inconnection with station I, the same including a standard 74 supporting aplatform 75 havinga special groove 76 formed in its top surface andwhich provides a ledge 77. The lever 78 is pivotally supported by thestandard 74, said lever being cam actuated and having a pivot connection79 at its top end with the push plate 80 which is slidable beyond theplatform 77. The push plate 80, in accordance with the invention, is adouble layered structure consisting of a top member 81 and a bottommember 82 having the bifurcated end providing the fingers '5 83. Topmember 81 pf the push plate rides over the ledge 77, whereas bottommember 82 rides over the platform 75 with one side of member 82 withinthe groove 76 below ledge 77. The mechanism at station C also includes achute 84 for continuously supplying the platform ledge 77 with end caps23 and which are deposited thereon when the push plate 80 is retracted.Platform structure also includes an extension bar 85 which terminates adistance beyond the drop off front of the ledge 77, said extension barserving as a positioning element 1 for the glass tube 22 as his indexedinto position at the station. The projection 86 on the front end of theplatform in alignment with the forwardly positioned extension bar 85contributes to the correct and uniform positioning of the glass tubeswhen loc'ated at station C for final capping.

The part holders 31 are simply indexed into position at station (3 andas-shown-i-n Figure 9 they are not elevated beyond their normal at restposition. Upon actuation of the lever 78 to deliver a cap, the pushplate 80 moves forwardly in a direction toward the right. The top member81 slides on the ledge 77 to push'a cap 23 toward the drop off front ofthe ledge while the bottom member 82 slides underneath the ledgetofinally embrace the glass tube which has been indexed into positionbetween the oppositelydisposed projections. While the glass tube is thusheld in proper position the cap 23 is pushed off the ledge 77 and isdeposited; over the'top of'the glass tube, being supported there by thefingered guide plate 82 which serves to maintain the cap over the end ofthe glass tube until final release. Said release takes place uponretraction of the guide plate 82, whereupon the cap drops into placeupon the glass tube.

With the completion of the operations at station C all the switchelements will have been assembled and there remains only the fusing ofthe end caps to the glass tube and the annealing of the completed unit.The next indexing movement of the turntable 30 progresses the assembledparts on holder 31 to station D which is blank to permit visualinspection of the assembled parts before subjecting the same toinduction heating at station E. Of course, it will be understood thatthe operations as described with respect to stations A, B and C takeplace simultaneously during the-period between indexing movements. Whena top cap is'being delivered to a part holder at station A, a glass tubeis being delivered at -B to another part holder which contains a topcap, and at C the bottom cap is being delivered to another part holderon which'has been deposited atop cap and glass tube. It will also'beappreciated that the various levers will be cam actuated in properrelation with each other and with the indexing movements of theturntable in order to accomplish the above operations, it being deemedunnecessary to show the cams for the levers as the same are conventionalin structure and in mode of operation.

T he mechanism of station E is shown in Figures l3, 14, 15 and 16. Thebase plate 88 supports the standard 89, having the platform '90 suitablysecured thereto in overhanging relation as by means of securing screws91. The base plate 88 also supports the cylindrical member 92. A secondstandard 93 supports .the platform 94, secured thereto by screws "95. Alifter, generally indicated by numeral 96, is located at station E andwhich issimilar in construction and mode ,of operationto the lifterdescribed in connection with station ,B. Said lifter 96 includes asupporting rod 97 mounted for vertical movement by thecylindrical member92. The lifter proper is provided with the jaws within which the spindle33 and terminal screw 72 of the part holder 31 are located when thesameis positioned at station E. However, the lifter, at this station isadditionally characterized by the transverse member 100 which issuitably fixed to the sup- ,porting rod 97 and positioned to project onrespective sides, of 'thefrod. The right hand projection is providedwith a plate 101 which'has associated relation-with the holding pin 102mounted by the cyiindricalmember 103 in the platform 94 for verticalreciprocating movement. The pin 102 projects some distance below member103 and below the platform 94, the said projecting portion beingprovided with the collar 104 having spaced flanges and said portion isalso provided with the flange 105' at the extreme lower end of the pin.The pin 102 is provided for the purpose of aligning the part holderswith the station mechanisms following each indexing movement ofturntable 30. As the lifter 96 is elevated from its position in Figure13 to its raised position, as shown in Figure 14, it will be understoodthat the pin 102 is caused to enter one of the openings 106, providedfor the purpose in the turntable. Such an opening is located inassociated relation with each part holder, being equally spaced aroundthe turntable as are the part holders so that insertion of pin 102 in anopening 106 at station B will operate to hold the turntable .in properindexed position with respect to the mechanisms at all the stations. Asthe lifter 96 is elevated the pin is raised by positive contact of plate101 with collar 104. -When lifter 9,6 is lowered at the end of aninduction heating operation the pin is resiliently withdrawn by theaction of the Urshaped spring 107 fixed to the underside of platform 94by the member 168 and which additionally functions as a guide for thefree end of spring 107. The said free end ,of spring 107 has associatedrelation with pin 102 between the flanges provided by the collar 104 andthus the pin is resiliently withdrawn upon lowering of lifter 96.However, positive action also takes place to withdraw the pin should thespring fail in its retracting operation since it will be seen that plate101 will eventually contact the flange lllS, thus withdrawing the pininto its retracted position as illustrated in Figure 13.

Transverse member 100 on the left side thereof is Provided with a plate110 which .is slotted at 111 for the reception of rod 112,. Said rod 112is pivotedto the lifter as at' 113 and the end 114 is disposed under thespindle 33, being adapted to have contact with terminal screw 72 in amanner and for purposes which will be presently described. The left endof rod 112 carries the Weight 115 which may be located in adjustedposition along the length of the rod to yieldingly bias the'end 114 inan upward direction. The purpose of the pivoted rod 112 is to apply ayielding force to spindle 33 and to its part holder 31. The part holderat station E is elevated as described in connection with holding pin102, said rod .112 having pivotal movement on axis 113 when the lifter96 is so elevated, causing a lifting of weight 115 .totheextent aspermitted by slot 111. This results from the downward force exerted byspindle 33 against end 114 as the lifter is raised from its lowposition, Figure 13, to its elevated position, as shown in Figure 14.During theinduction heating operation the action of end 114m applying ayielding upward force tospindle 33 and thus to its part holder is tomaintain the parts of the switch structure in firm contact whereby tofacilitate joining .of the end caps to the glass tube during thissealing operation, and in part to control the finished dimensions of theswitch. The above action of the weighted rod 1-1'2takes place inconjunction with a weighted top cap holder, which structure will now bedescribed in detail.

Platform 90 is provided with the collar 118 which extends through theplatform, being suitably secured thereto by the locking nuts 1 19. Thecollar mounts the bearing sleeve 120 for verticalreciprocatingmovement'so that the sleeve moves toward and from the part holders 31.The top projecting end of bearing sleeve 120 'is provided with a weight121 in the form of a cup-shaped housing, the same being secured to thatend ofthe sleeve projecting immediately above collar 118. A shaft 122 isdisposed within the bearing sleeve and which is of a lengthsubstantially equal to that of the sleeve. The weight 123 issuitably-secured to the top end of shaft 122 and said :shaft atits lowerend'has fixed thereto a direction.

i 7 top cap holder 124, there being provided above the holder the limitnut 125, which is adapted to contact the end of sleeve 120 under certainconditions to cause upward movement of the sleeve and elevation of thehousing 121. When the assembled parts of the present switch areyieldingly held between the cup member 32 and the top cap holder 124 thesame will be properly positioned with respect to coils 126 and 127,Figure 16, of a conventional induction heating device generallyindicated by numeral 128, Figure 1, said coils having connection withthe device through terminals 129. The device 128 has connection with asource of electric current through lead L and L and said device suppliesthe coils 126 and 127 with high frequency alternating current in thevicinity of 27 to 28 megacycles, although this may vary depending on thenature of the seal being made. A powerful alternating current'field isthus created in the immediate vicinity of the end caps 21 and 23, sinceit will be observed that the top coil 126 of the induction device ishorizontally positioned with respect to the bottom cap 23, whereas thebottom coil 127 is horizontally positioned with respect to the top cap21. The holders, including the cup member 32 and the top cap holder 124,are made of ceramic material so that they are not affected by the highfrequency electric field. However, as is well known in the art ofinduction heating, the metal of the end caps is heated to a hightemperature and also due to the dielectric losses in the glass of thetube the said glass will also 'be heated. However, only the top andbottom edges will attain a fusion temperature primarily due to thereflection of the heat from the end caps. The heating of the glass to asoftening temperature is attained rather quickly and fusion of theswitch parts accordingly takes place. However, during this action thesaid switch parts are under yielding pressure by reason of weight 123acting downwardly through shaft 122 on the top cap holder 124, and,further, as a result of the weight 115 acting upwardly through the leverend 114 and spindle 33 on the cup member 32.' The mode of operation ofthe weighted parts will now be described.

It will be observed by reference to Figure 13 that a gap, indicated bythe space S, exists between the end of sleeve 120 and the limit nut 125.It will also be observed that the slot 111 has a definite length forlimiting the pivotal movement of the weighted rod 112. As the lifter 95is elevated to position the assembled switch elements for the inductionheating operation the cap 23 will engage the top holder 124 which isyieldingly biased into its extreme downward position by the weight 123and thereafter rod 112 will be rotated in a direction to elevate weight115.

rendering the same operative through end 114 to yieldingly bias thespindle 33 and the part holder in an upward Continued upward movement ofthe lifter will move the top cap holder upwardly into engagement withthe cap holder 124, effecting elevation of the weight 123, whichmovement can continue to the extent of gap S. When the space representedby gap S has been taken up further movement of the lifter will cause theweighted bearing sleeve 120 to *be elevated, in which position it isclamped in a manner hereinafter described. When the parts assume thisposition the induction heating operation can be initiated. As the endcaps reach a high temperature and the top and bottom edges of the glasstube become soft the top cap holder and the cup member, both weighted ina direction to cause movement toward each other, exert their force uponthe heated switch structure. This maintains the parts in finm contactand in addition limits shrinkage in one instance to the extent of gap Sand in the other instance to the extent of the slot 111, taking intoconsideration the movement of end 114, due to the lever ratio. As aresult the overall length of the completed switch is controlled.

The mechanism at station E additionally includes switch means forstarting the induction heating operation after the parts have beenproperly positioned with respect to the coils and after gripping byspring energized jaws for the purpose of holding the switch structureand steadying the same during the heating step. The platform hassuitably secured thereto a bracket which carries the mercury switch 131at its right hand end, said switch being releasably held to the bracketthrough the instrumentality of the spring clips 132. The said switch 131is connected to the control circuit L and L, of the induction heatingdevice 128 so as to control the supply of electric current thereto.Actuation of the switch is effected by means of a magnet 133 fixed toand carried by arm 134 which is mounted for oscillating movement sincethe arm is suitably fixed to the vertically disposed shaft 135.

The shaft 135 is journalled for rotation, being mounted at its top endin the collar 136 in platform 90 and at its terminal lower end in thebase member 137. As best shown in Figure 15, the left hand end of thearm 134 is in engagement with the set screw 138 carried by arm 139 ofthe cam actuated lever 140. Said lever 140 and arm 139 are suitablysecured to pivot shaft 141 extending vertically in parallel relation tostandard 89 and being mounted for rotation by the platform 90 at its topend and by support 142 at its lower end, Figure 13. The cam 143 isadapted to actuate cam lever 140 to eflect oscillating movement of arm134 whereby the magnet 133 is positioned close to switch 131 or isretracted, being spaced therefrom. When the magnet is located close tothe switch the switch is effective to close the electric circuit to theinduction heating device, rendering the same operative.

Simultaneously with the closing of the switch 13 spring energized jaws,including the top pair 144 and the bottom pair 145, are caused to closeto resiliently engage the bearing sleeve 120 and the glass tube 22,respectively. In accordance with the invention shaft 135 is providedwith an intermediate flat blade portion 146, the said portion extendingabove jaws 144 and below jaws 145 and being disposed between the jaws ofeach pair. On respective sides of the jaws there is provided a platemember such as 148 and 150, the said plates being suitably secured withcap screws 153 to the platform 96 so as to depend therefrom, andproviding the support for the base member 137. The rods 151 for the pairof jaws 144 and the rods 152 for the pair of jaws 145 extend throughtheir respective jaws to project on opposite sides thereof and said rodsalso extend through the plate members 148 and 150. Collars 154 aredisposed on the rods on both sides of their jaws and said collarsprovide seats for the coil springs 155 which are confined between saidseats and their respective plate members. As a result of the structureabove described, each pair of jaws 144 and 145 is resiliently urged in aclosing direction as a result of which the left end of the jaws willhave clamping action with respect to their particular element. However,each pair of jaws is normally held in an open separated relation as aresult of the flat blade portion 146 which is normally positioned so asto cam the jaws into said open spaced relation. When cam 143 has rotatedto where the cam portion 156 is in contact with roller 157 of the lever140 the action is such as to allow arm 134 to rotate the blade portion146 parallel to the jaws to bring magnet 133 into close proximity toswitch 131. The arm 134 has a natural tendency to rotate in thisdirection due to the resilient biasing action of springs 155 on the fiatblade portion 146. Accordingly, it'will be seen that when switch 131 isclosed to start operation of the induction heating device the fiatportion 146 will simultaneously assume a position parallel to the jawsof each pair, allowing the jaws to close under the tension of coilsprings 155. Therefore upon initiation of the induction heating thebearing sleeve 120 and the glass tube 22 are gripped by the jaws 144 and145 respectively so that the force applied to each of the caps by theweights 115 relation.

ncreases and 123, as previously described, isrto the degree limited onlyby the extent of the slot 111'in lifter'i96 an'dt he gap S establishedwith respect to the movement ofzweight 123. By holding =the glass andthe sleeve, the force of weight 115 is applied only to the bottomcapwhile the force of weight 123 .is applied'only to the upper cap..Moreover, since sleeve 120 is movable heyond the limited independentmovement of the-shaft 122, it is necessary to prevent movement-of thesleeve during the gauged movement of the weight-123.

Whereas, the induction heating. operation is initiated by closing theterminals of the magnetic switch 131, it will be understood that saidoperation is terminated'by the heating device itself which employstiming mechanism ;for accurately timing the duration of. the heatingperiod.

The mechanismat station B will remaininthepositions assumed during theheating step untilcam143 has rotated to actuate cam lever140 andoscillate lever 134 to with- .draw magnet133 from themagnetic switch131.Opening of the switch occurs simultaneously with rotation of ;the fiatblade portion 146-to cause opening ofthe jaws.

The space between the two pairs ofjaws accommodating lowpositiomtheholding pin 102 i s simultaneously withdrawn from its'opening in theturntable. .The turntable cannow be indexed to progress the work holderswith -respect to all the stations and the assembled switch previously atstation E is moved to station P .where it is subjected to gas fiamesproduced by the gas jets158. Similar gas jets are located at station Gand at :station H so that for the next two indexing movements of theturntable the assembled switch housing will be subjected .to gasfiames'for the purpose of annealing the, glass tube of the housing.Station I is blank and at station K the ,switch housing isdischarged'uponactuation. of the lever 460. The switch housing isnowreadyfor thefiushing operation and for the injection of mercury,whereupon a .iinabsealing operation completes themanufacturingoperations on the switch.

The apparatusforflushing the interior of the switch 'housingandinjecting mercury into the, same-is shownin {Figure 2. The member 161 iscored at 162 and pro- ,yidedswith nipple 163 adaptedto connect withasupply ofrgassuch as. hydrogen and the like. A similar cored ,pas'sage164 is also formed in member 161, towhich is .joined the connectionlfiSleading to a supply of mercury. 'Member -161 additionally forms a baseand ,supporting structure for a needledike projection indicated in its Ientirety by numeral 166 and whichcomprises three separate 1 tubes ofrelatively small size each of which is Qfiattened to providetwo flatsurfaces at anangle of approximately 120 degrees. fso formed arethenplaced together and drawn through The three lengths 1 of tubing acollar 167 which functions to hold them in assembled Below the collareach length of tubing is separated tromthe otherto providethreeextremities, one

of which,.narnely, .168, is anchored in member1'61, to havecommunicating relation with passage16 2. Another .length oftubing170 issimilarly anchored in member 161 andhas communicating relation withpassage 164. The third length of tubing, namely, 171, terminates abovemember 161 and accordingly communicates with the atmosphere. The opening26, as previously described in connection with the bottom cap 23, isrelatively small'in 'size although large enough to receivethe tripledtubed, needle-like projection 166, whichmeasures approximatelyone-thirty-second inch'in diameter. The next operation on theswitchhousing is to place the same on the 'pro- J jection =166 with the:projection extending 'well inside the 'switch structure. .The flushingoperation is initiated hy admittinggas-throughthe gas passage-162, thesame :fiowing through tubing 168 to enter the switch housing. Since thegas is under pressure'it will force the air from the housing,'whichair-is conveniently vented through tubing 171 and discharged to theatmosphere. After theinterior of the switch has been adequately flushedthe gas is valved off and a metered. quantity of mercury -is injectedthrough tubing 176. switch is then removed from the needle projection166 and inaccordance with the invention the mercury will close opening26 since the opening is small enough in The mercury loaded size toprevent release of the mercury. Accordingly,

the mercury forms a seal, closing off opening 26 and trapping the gaswithin the switch housing. The switch is held'ina positionwherein themercury seals the opening until an iron pin suchas 28 is inserted in theopencury'for the purposeof reducing the contact resistance between themercury and the end cap, which become ing and welded to hermeticallysealthe switch. The iron pin su'ch as 28 may project some distance intothemeroxidized during the sealing operation. In those cases whereresistance is an important factor with respect to the use of the switch,special metals and other means may be employed to insure good contactbetween the mercury, electrode and end cap.

The -switch 20 is now complete and ready for use.

When interposed in an electric circuit the same will 'open'th'e'circuitwhen tilted so that the mercury flows out of contact with metal cap '23.However, the circuit will be closed through the switch when the same istilted so that the mercury fiows into the'end cap 23 and additionallymaintains contact with electrode 24. The product of the inventioncomprises a miniature switch of the mercury type which may be as smallas ninesixteenths of an inch in length with a maximum diameter ofthree-'eights of an inch. Such a switch Will have many uses in theautomotive and appliance field. The

advantages of themetal to glass seal, together with the machine methodof assembling the component parts of the switch, and the simplifiedmethod of flushing with gas and injecting mercury, results in theproduction of a mercury switch wherein the length of the switch is notany greater than that needed to enclose operative switch structure. Inaddition the cost of manufacture is-greatly reduced in comparison to thecost when old methods are employed. It is to be-recognized that theinvention may be employed in the manufacture of switches of larger size,the size changebeing that resulting from the character of the "switchparts necessitated by the current capacity rating of the switch and theoperating methodof theswitch structure. Furthermore, the basicprinciples of switch manufacture covered by this invention makespossiblea simplified and less costly manufacture of switches incorporatingmechanisms sensitive to the high temperatures attained in the sealingoperations, all

of which can afiect the operating characteristics of calibrated andadjusted segments of the operating structure made prior to-the finalsealing operation.

In connection'with the foregoing, reference is made to Figures 5 and 6which illustrate certain manufacturing procedures designed especiallyfor mercury switch structures of the magnetic type wherein a springactuated-electrodeis supported from one of the metal end caps. In

-magnetic switch structure of this type the spring actuated electrode isproperly adjusted for a particular operation,

and it will be appreciated that upon being subjected to "intense heatits operating characteristics could be materially changed since heatwill affect the tension of the spring and also the strength of themagnet mounted upon the springactuatedelectrode. According to the methodof the invention a metal end cap 172 can be fused to the:glass'container 173 by means of induction heating efifected throughcoils 1 74 which are'suitably energized by the induction heatingdevice175, under control of switch 131, all as shown in Figure 5. Theoperating switch mechanism, generally designated by numeral 176, can besecured to the electrode stem such as 177, fixed to and protruding fromthe metal end cap 172. After adjustment of the switch mechanism a secondend cap 178 is applied to the opposite end of the tube and the switchstructure 180 is again subjected to induction heating which, in thisinstance, is confined to the end cap 178. This last induction heatingoperation requires that the switch structure be inverted, all as clearlyshown in Figure 6. As a result the heat sensitive mechanism of theswitch is removed from the area where heating takes place for fusing thefinal cap to the glass tube. With the heat being localized, and theheating period of relatively short duration, it will be understood thatthe critical parts of the switch are accordingly not injured byexcessive heat. Following the completion of this last fusing operationthe switch housing is flushed in a manner as explained in connectionwith Figure 2, for which purpose the metal end cap 178 is provided witha small opening, the same as end cap 23. Mercury is then injected intothe switch structure and following this operation the opening in themetal end cap 178 is sealed by inserting a metal plug and welding thesame in place.

The invention is not to be limited to or by details of construction ofthe particular embodiment thereof illustrated by the drawings, asvarious other forms of the device will of course be apparent to thoseskilled in the art without departing from the spirit of the invention orthe scope of the claims.

What is claimed is:

1. In the manufacture of a mercury switch wherein metal end caps aresealed to respective ends of a glass tube, the steps which include theassembling of the parts by placing a glass tube on a bottom cap anddepositing a top cap on the opposite end of the tube, subjecting theassembled parts to induction heating to fuse the glass tube to the metalend caps whereby to provide a unitary switch housing, flushing theinterior of the switch housing by injecting a gas into the housingthrough an opening in one of the end caps, then injecting a quantity ofmercury into the switch housing through the same opening, and finallyclosing said opening while the same is sealed by the mercury byinserting a member therein and welding the member in place.

2. In the manufacture of a mercury switch wherein metal end caps arehermetically sealed to respective ends of a glass tube, the steps whichinclude the assembling of the parts by depositing a glass tube on abottom cap and then depositing a top cap on the opposite end of thetube, subjecting the assembled parts to an induction heating tohermetically join the glass tube and the metal end caps whereby toprovide a unitary switch housing, flushing the interior of the switchhousing by injecting a gas into the housing through an opening in one ofthe end caps and simultaneously therewith discharging the air from theswitch housing through the same opening, then injecting a quantity ofmercury into the switch housing through said opening, and finallyclosing said opening while the same is sealed by the mercury byinserting a member therein and welding the member in place.

3. In the manufacture of a mercury switch wherein metal end caps arehermetically sealed to respective ends of a glass tube, the steps whichinclude the assembling of the parts, subjecting the metal end caps toinduction heating while holding the parts in assembled relation, wherebyto hermetically join the metal end caps to the glass tube and provide aunitary switch housing, flushing the interior of the switch housing byinjecting a gas into the housing through an opening in one of the endcaps and simultaneously therewith venting the air from the switchhousing through the same opening, then injecting a quantity of mercuryinto the switch housing through said opening, and finally closing saidopening while the 'sameis sealed by'the mercury by inserting a metalplug therein and welding the metal plug in place.

4. In the manufacture of a mercury switch wherein metal end caps arehermetically sealed to respective ends of a glass tube, the steps whichinclude the assembling of the parts, subjecting the metal end caps toinduction heating while holding the parts in assembled relation,applying pressure to force the end caps into contact with the glass tubeduring the induction heating step whereby to hermetically join the metalcaps to the glass tube and provide a unitary switch housing, flushingthe interior of the switch housing by injecting a gas into the housingthrough an opening in one of the end caps and simultaneously therewithventing the air from the switch housing through the same opening, theninjecting a quantity of mercury into the switch housing through saidopening, and finally closing said opening while the same is sealed bythe mercury by inserting a member therein.

5. In the manufacture of a mercury switch wherein metal end caps arehermetically sealed to respective ends of a glass tube, the steps whichinclude the assembling of the parts by bringing them into juxtaposedrelation in the proper order, subjecting the metal end caps to inductionheating while holding the parts in assembled relation, applying pressureto each end cap to force the same into firm contact with the glass tubeduring the induction heating step, controlling the pressure to controlthe shrinkage of the glass tube due to the fusion taking place at theends thereof with the metal end caps, whereby the parts are hermeticallyjoined and a unitary switch housing is provided, flushing the interiorof the switch housing by injecting a gas into the housing through anopening in one of the end caps and simultaneously therewith venting theair from the switch housing through the same opening, then injecting aquantity of mercury into the switch housing through said opening, andfinally closing said opening while the same is sealed by the mercury byinserting a member therein.

6. In the manufacture of mercury contact switches, the method ofassembling the parts of the switch housing by machinery including stepby step movements wherein the first step consists in depositing a metalend cap on a part holder at the first station of said machinery, movingthe part holder to the next station by an indexing operation, depositinga glass tube onto the metal end cap so that the parts are in properjuxtaposed relation for closing the bottom end of the tube, againindexing the part holder to the third station, placing a second metalend cap on the glass tube to close the top thereof and simultaneouslyholding the glass tube to assure proper positioning thereof, againindexing the part holder to locate the assembled switch parts at anotherstation, fusing the metal end caps to the glass tube by subjecting theend caps to an ultra high frequency electric discharge, applyingyielding pressure to the end caps respectively to press them intocontact with the glass tube during the fusing step, then indexing thepart holder through successive stations for subjecting the switchhousing to an annealing process by directing gas flames against theglass tube, and finally removing the completed switch housing fromv thepart holder.

7. Apparatus for use in the manufacture of mercury switches of the typewherein metal end caps are sealed to respective ends of a glass tube,the combination with mechanisms located at various stations, of aturntable adapted to be periodically indexed with respect to saidstations, a plurality of part holders carried by the tumtable and whichare moved from station to station by said indexing of the turntable, themechanism at one station comprising means for depositing an end cap on apart holder, the mechanism at the next station comprising means forplacing a glass tube on the said end cap, the mechanism at the nextstation comprising means for depositing another end cap and for placingthe same on the top end of said glass tube, and mechanism at stillanother station for fusing the end caps to said glass tube, said lastmentioned mechanism including a top cap holder adapted to contact thesaid top end cap for holding the assembled switch parts between the sameand the part holder, and said last mentioned mechanism additionallyincluding induction heating coils and a high frequency electric devicefor energizing the coils, said holders presenting the as sembled switchparts to said coils to effect an induction heating of the end caps forfusing said caps to the respective ends of the tube.

8. Apparatus for use in the manufacture of mercury switches as definedby claim 9, wherein said last mentioned mechanism aditionally includesspring energized jaw members for gripping and holding the glass tube ofthe assembled switch parts during the fusing operation, a rotatableblade member for effecting opening and closing action of the jawmembers, an electric switch for initiating operation of the highfrequency electric device, and means fixed to and actuated by the blademember for controlling the operation of said electric switch.

9. Apparatus for use in the manufacture of mercury switches of the typewherein metal end caps are sealed to respective ends of a glass tube,the combination with mechanisms located at various stations, of aturntable adapted to be periodically indexed with respect to saidstations, a plurality of part holders carried by the turntable and whichare moved from station to station by said indexing of the turntable, themechanism at one station comprising means for depositing an end cap ontoa part holder, said means including a platform having a groove, amagazine feed supplying said end caps to said groove and a push plateslidably mounted in the groove for reciprocating movement, the mechanismat the next station comprising means for placing a glass tube on thesaid end cap, the mechanism at the next station operating to depositanother end cap and place the same on the top end of said glass tube,said mechanism including a platform having a groove, a magazine feed forsupplying the last mentioned end caps to said groove, a push plateslidably mounted in the groove for reciprocating movement, said pushplate including top and bottom members, the bottom member having abifurcated forward end whereby the end cap delivered to the drop offedge of the platform by the top member is deposited onto the bottommember which places it on the glass tube upon retraction of the pushplate, and mechanism at still another station for fusing the end caps tosaid glass tube, said last mentioned mechanism including a top capholder adapted to contact the top end cap for holding the assembledswitch parts between the same and the part holder, and said lastmentioned mechanism additionally including induction heating coils and ahigh frequency electric device for energizing the coils, said holderspresenting the assembled switch parts to said coils to effect aninduction heating of the end caps for fusing said caps to the respectiveends of the tube.

10. Apparatus for use in the manufacture of mercury switches of the typewherein metal end caps are sealed to respective ends of a glass tube,the combination with mechanisms located at various stations, of arotatable turntable adapted to be periodically indexed with respect tosaid stations, means operative at the end of each indexing operation forlocking the turntable in position, a plurality of part holders carriedby the turntable and which are moved from station to station by saidindexing of the turntable, the mechanism at one station comprising meansfor depositing an end cap onto a part holder, said means including aplatform having a groove, a magazine feed supplying said end caps tosaid groove and a push plate reciprocable in the groove for feeding theend caps individually, the mechanism at the next station comprisingmeans for placing a glass tube on the said end cap, the mechanism at thenext station operating to deposit another end cap and place the same onthe top'end of said glass tube, said mechanism including a platformhaving a groove, a magazine feed for supplying the last mentioned endcaps to said groove, a push plate reciprocable in the groove for feedingthe said end caps individually, said push plate including top and bottommembers separated by a platform ledge, the bottom member having abifurcated forward end whereby the end cap feed to the terminal end ofsaid ledge by the top member is deposited onto the bottom member whichplaces it on the glass tube upon retraction of the push plate, andmechanism at still another station for fusing the end caps to said glasstube, said last mentioned mechanism including a top cap holder adaptedto contact the top end cap for holding the assembled switch partsbetween the same and the part holder, said last mentioned mechanismadditionally including induction heating coils and a high frequencyelectric device for energizing the coils, said holders presenting theassembled switch parts to said coils to effect an induction heating ofthe end caps for fusing said caps to the respective ends of the tube,and yielding pressure means combined with said holders respectively forapplying yielding pressure to the end caps to force them into contactwith the glass tube during the fusing operation.

References Cited in the file of this patent UNITED STATES PATENTS1,895,177 Staley Jan. 24, 1933 2,048,556 McArthur July 21, 19362,101,092 Payne Dec. 7, 1937 2,160,367 Maxfield May 30, 1939 2,210,017Wetherby-Williams et al. Aug. 6, 1940 2,298,178 Staley Oct. 6, 19422,305,414 Gerisch Dec. 15, 1942 2,324,595 Pollard July 20, 19432,482,734 McKenzie et al Sept. 20, 1949 2,522,990 Cartun Sept. 19, 1950

